Inkjet printheads are non-contact fluid ejection devices that eject ink from printhead nozzles onto a media substrate (e.g. paper) to form an image. Thermal inkjet printheads eject drops from a nozzle by passing electrical current through a heating element to generate heat and vaporize a small portion of the fluid ink within a firing chamber. Piezoelectric inkjet printheads use a piezoelectric material actuator to generate pressure pulses that force ink drops out of a nozzle. While both dye-based and pigment-based inks are used in inkjet printheads, properties such as color, jettability, drying time, long term storage stability, and decap time (the amount of time a printhead can be left uncapped and idle and can still fire ink droplets properly), influence which type of ink is used in a particular printhead.
Pigment-based inks are increasingly used over dye-based inks because of the various advantages they provide, such as color strength and water fastness. Pigment particles are larger and remain in suspension rather than dissolving in liquid. This provides greater color intensity as the pigment inks remain more on the surface of the paper instead of soaking into the paper. Pigment inks also tend to be more durable and permanent than dye inks. For example, pigment inks smear less than dye inks when they encounter water.
Unfortunately, pigments (colorant particles) suspended in the ink vehicle/carrier tend to settle when a printhead is not used for an extended period of time. Pigment settling can cause printhead nozzles to clog, which reduces the overall print quality.